Compact discs (CD's)are widely used for storing both audio and visual information in digital form. Compact discs are discs which consist of a disc of plastic having a thickness of about 1 mm to 1.5 mm and typically have a diameter of about 4 3/4. Other types of discs such as digital videodiscs (DVD's) have a smaller digital information band. The information, in digital form, is recorded on an information layer which consists of a continuous spiral data track. After the data is placed on the disc, a metallic film is placed over the data and it is sealed with a protective layer. Damage to the information layer can occur if scratches or other surface blemishes occur in the plastic protective layer. CD's generally have a data track on one side while some disc such as DVD's store data on both sides.
Reading of discs is accomplished by a laser beam which scans the disc through the plastic protective layer. The laser is reflected by the metallic film. Damage, as mentioned, to the protective layer will interfere with the scanning process such that tracking errors or distortion will occur when the disc is played.
Even relatively small scratches or blemishes resulting from handling of the disc can lead to disturbances in faulty reproduction. The laser reading beam scans the data track and blemishes, imperfections and scratches in the protective layer which is generally a polycarbonate, will hinder the laser's ability to properly read the data and "skips" will occur.
The prior art discloses various methods and apparatus for refinishing CD's.
U.S. Pat. No. 5,220,754 shows a method for restoring compact discs in which the disc is held and a scraping action is applied to the coating on the disc.
U.S. Pat. No. 5,571,041 discloses a method for repairing and refinishing audio and video CD's. The top side of the disc is placed against a soft, covered wheel and secured to the wheel. The disc is spun on low rpm and a heavy cut cleaner applied across the surface of the bottom side of the disc using a clean cotton cloth or pad. This step is repeated at higher rpm using a medium cut cleaner and then a finer cut cleaner. Clear plastic cleaner and a clear plastic polish are then applied using a cotton pad.
U.S. Pat. No. 5,207,759 discloses a method for texturing a disc using a slurry. The slurry includes different sized particles, preferably a first in the 3 micron size range and a second in the 1 micron size range. Particles are used to abrade the surface of the disc. A pad is moved relative to the disc to scour the substrate.
U.S. Pat. No. 5,167,096 discloses a method and apparatus for texturing a substrate. A texturing pad and the disc are rotated about parallel, offset axis and pressed against one another in the presence of a particle slurry. The inner, less compressible region of the pad produces a deeper grooved texturing on an inner, annular surface of the disc.
U.S. Pat. No. 5,099,618 discloses a method for repairing damaged recording discs by removing a part of the protective layer in directions cutting across the data track path.
U.S. Pat. No. 4,179,852 relates to a method and apparatus for polishing a floppy disc. The floppy disc is placed on a circular, resilient pad disposed on a first spindle-mounted circular platen. A circular, fibrous or abrasive polishing disc is disposed on a second spindle-mounted circular platen. The radius of the polishing disc is greater than the width of an annular region to be polished on the disc so that the relative velocities between points on the polishing disc and the points on the floppy disc are uniform. In the apparatus of this patent, the floppy disc and polishing disc are rotated in the same angular direction at first and second velocities.